The present invention is directed to an apparatus and method for fluid injection for prolonged delivery and uniform distribution of reagents into plasma. In particular, the present invention is directed to an injector for deposition of protective coatings on various substrates such as glass, quartz, metal or metallized materials, and plastics.
The use of a polycarbonate (PC) sheet or film for outdoor applications such as architectural glazing and automotive glazing requires the PC to be protected from the abrasion effects. Thus, an abrasion resistant coating is conventionally formed on PC.
Various conventional deposition techniques for abrasion resistant coatings have been developed. For example, chemical vapor deposition (CVD), physical vapor deposition (PVD) and plasma-enhanced chemical vapor deposition (PECVD) are widely used. PVD produces solid films by supplying thermal energy to activate the source material for deposition. CVD produces a solid film on a substrate surface by thermal activation and surface reaction of gaseous reagents which contain the desired constituents of the film. Energy required to activate the reactants is supplied by heating the substrate. For reasonable reaction rates the substrate is heated to relatively high temperature, in the range of about 500 to 2000xc2x0 F. PECVD supplies energy to the reactants by an electrical discharge in a gas which forms a plasma in the deposition chamber. With the help of plasma, substrate heating is no longer needed and low melting point materials such as plastics can be coated in a straightforward manner by using PECVD.
An important component in these deposition systems is the device used to inject reagents, metal vapors, and other source materials into the plasma stream. For example, U.S. patent application No. 09/033,862, filed Mar. 3, 1998 (pending) and U.S. Pat. No. 6,110,544, issued on Aug. 29, 2000 describe a nozzle-injector for high-rate, large-area deposition using an arc plasma.
Conventionally, a series of orifices (also referred to as injectors) evenly distributed over an injector body or plate are used for controlled, uniform delivery of gases or vapors over an area. Such a device is sometimes referred to as a showerhead injector or distributor. High and even flow resistance at every injector is desirable to ensure uniform distribution of an injected reagent throughout all injectors.
For example, a conventional narrow, straight-walled injector is shown in FIG. 2 as injector 20. Often, a reagent interacts with the plasma 18 near the exit aperture, such as aperture 22, and thus reagent is deposited as a solid layer 19 not only at aperture 22, but also along inner wall 24. When utilized in a multi-channel reagent injection device, clogging can occur unevenly among the orifices, thus the uniformity of reagent delivery (and subsequent deposition) is hampered. Also, the performance of the injector can vary as a function of time, and frequent cleaning of the clogged injectors is necessary.
Thus, although a showerhead injector is effective for uniform distribution of reagents, it suffers from a general shortcoming of orifice clogging during prolonged exposure to condensable reagents, especially in the presence of plasma. This occurs because the concentration of the reagent is high at the injector exit aperture, and because the injector is often in contact with the plasma. High reagent concentration combined with plasma activation encourages deposition of a solid film at the injector exit aperture and on the inner walls of the injector. As a result, the injector becomes clogged over time. If clogging occurs unevenly among the injectors, the uniformity of material delivery is hampered. A clogged injector needs to be cleaned or replaced, thus causing process interruption, adding down time and operating cost.
In view of the foregoing, it would be desirable to provide an apparatus for injecting a fluid into a plasma stream with a uniform distribution and with reduced likelihood of clogging over prolonged use.
The present invention provides an injector system that includes a base containing an injector. The injector comprises an inner wall defining a first channel portion for restricting a flow of the fluid and having a shape such that the inner wall of the first channel portion is parallel to a first axis. The injector also includes an inner wall defining a second channel portion in fluid communication with the first channel portion. The second channel portion includes a recessed portion such that the inner wall of the second channel portion diverges from the first axis at a predetermined angle. The second channel portion reduces a buildup of a clogging layer on the inner wall of the second channel portion over a period of use. In addition, the injector can further include a tip portion that protrudes into the plasma.
In view of the foregoing, it would also be desirable to provide an apparatus for coating a substrate.
According to another embodiment of the present invention, an apparatus for coating a substrate includes a plasma generator having an anode and a cathode capable of forming an arc plasma that travels toward a substrate, a chamber to house the substrate, and a first injector system located between the anode and the substrate for introducing a first reactant into the plasma. The first injector system comprises an injector that includes a first channel portion for restricting a flow of the fluid and having a shape such that inner walls of the first channel portion are parallel to a first axis. The injector also includes a second channel portion in fluid communication with the first channel portion. The second channel portion includes a recessed portion such that inner walls of the second channel portion diverge from the first axis at a predetermined angle. The second channel portion reduces a buildup of a clogging layer on the inner walls over a period of use. In addition, the injector can further include a tip portion that protrudes into the plasma.
In view of the foregoing, it would be desirable to provide a method for injecting a fluid into a plasma stream with a uniform distribution and with reduced likelihood of clogging over prolonged use.
According to another embodiment of the present invention, a method of coating a substrate in a uniform manner comprises supplying a first reactant to an injector system having a plurality of injectors disposed along a circumference of a fluid supply channel, where each of the injectors includes a first channel portion and has an orifice with a diameter sufficient to restrict a flow of the first reactant and a second channel portion being a recessed portion, such that inner walls of the second channel portion diverge from a first axis at a predetermined angle to reduce a buildup of a clogging layer comprising the first reactant on the inner walls. An arc plasma is generated. The first reactant is introduced into the plasma and the first reactant is deposited on a surface of the substrate.
In view of the foregoing, it would be desirable to provide an article having a coating deposited using the apparatus of the present invention.
According to another embodiment of the present invention, a coated article coated by the apparatus of the present invention comprises a substrate having a surface and at least one coating deposited by plasma assisted chemical vapor deposition on the surface.
Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings.